Friday, November 30, 2018

Implications of water quality on coffee

Thanks to Jeremy for reminding me about the importance of water quality on coffee. Indeed, I have mentioned before that water quality affects beverage quality - think coffee, tea, coca cola etc. - posts 1, 2. People like Starbucks and Coffee Bean not just for their ambience and branding. These coffee joints sell good coffee using quality coffee powder/beans plus that very critical yet often unseen ingredient - water of consistently good quality.

Figure: My favourite kind of beverage - tea with milk aka teh in SG parlance. How often do we consider that water quality can affect the taste of this ubiquitous beverage?

Unlike a coca cola factory or even a commercial café, most of us mortals would not bother to purchase the filtration equipment necessary to produce water of consistently good quality. The next question is: what do you mean by good quality water? As I always maintain, water quality must be tied to the purpose of the water. Tap water of course has relatively stringent requirements (at least in developed countries). In SG, we generally follow WHO drinking water guidelines.

But what about coffee? How does one define water quality guidelines for coffee (or tea or coca cola for that matter)? Obviously, the guidelines (if there are any) must be above and beyond those of drinking water.

For example,
Figure: SCAA/SCAE (Specialty Coffee Association of America/ SCA of Europe) guidelines in water quality for coffee making
A few points to keep in mind:
  1. Coffee quality in terms of taste and smell are obviously subjective. Therefore, such subjectivity extends to the water quality requirements as well.
  2. How comprehensive are the above guidelines? I see only 8 parameters. WHO has about 200 parameters in its drinking water guidelines. How would other WQ parameters (e.g. fluoride, metals) affect the quality of coffee?
  3. For us in SG, how well does our tap water compare against the above values? Let's take a look.

  1. Odour - unobjectionable. No issues here.
  2. Colour < 5 Hazen units. Should not be an issue here.
  3. Total chlorine 1.70-2.80mg/L. Hmmm... possible issue since our tap water MUST HAVE a certain amount of residual chlorine.
  4. TDS (total dissolved solids) 74-269mg/L. More or less falls within the SCAA guidelines.
  5. Total hardness 27-221mg/L as CaCO3. This of course includes calcium and other forms of hardness so we can't tell for sure. But if your tap water happens to be near the higher end of the range, you may have a problem as compared to the SCAA guidelines for calcium hardness.
  6. Total alkalinity 6-40mg/L as CaCO3. If your tap water is near the lower end, you may have too little alkalinity to neutralise the acidity in your coffee. But then again, it depends on how acidic you like your coffee.
  7. pH 7.8-8.3. Compared to the SCAA guidelines, is our tap water too alkaline for coffee?
  8. No value given in the report as it is not a priority pollutant for drinking water.
Finally, our tap water quality cuts across a range of values though it should still stay within specs. With so many different sources of water (various water treatment plants and reservoirs with and without desalted water mixed in), it is no surprise that the actual water quality parameters can change from time to time and area to area.

Therefore, if you are really serious about producing consistently good quality coffee, you need good quality filtration equipment to treat your tap water (in addition to other good quality ingredients of course). I leave the cost/benefit analysis up to you to evaluate.

Figure: Everpure water filter kit for coffee brewers. Only for illustration purposes. Not an endorsement or recommendation.

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